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Thales -- 620 BCE-546 BCE
Thales was the investigate the basic principles (atom). His atomic model was based on human senses. -
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Democritus -- 440 BCE
Democritus created the first atomic theory. He came up with the word 'atom'. -
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Aristotle -- 340 BC
Aristotle didn't believe in the atom, because it put restrictions on gods. He believed in the four elements: fire, air, water, earth. -
Sir Isaac Newton
Newton believed that matter is formed of solid, massy impenetrable particles and atoms are held together by attractions or forces. -
John Dalton
Dalton had the atomic theory experiment. His atomic theory was:
1. All matter is made up of tiny particles called atoms.
2. All atoms of a given element are alike, but are different from the atoms of any other element.
3. Compounds are formed when atoms of different elements combine in fixed proportions.
4. A chemical reaction involves a rearrangement of atoms, not a change in the atoms themselves. -
Becquerel
Becquerel discovered radiation using the uranium experiment. -
J.J. Thompson
Thompson used a cathode ray tube to discover electrons. He discovered the plum pudding model. -
Milliken
Milliken used the Oil Drop Experiment to find the charge of individual electrons. -
Gold Foil Experiment
Alpha particles were fired through a thin gold sheet into a zinc sulfide sheet. Rutherford found a portion of the atom was positively charged and relatively heavy. -
Rutherford
Rutherford used the Gold Foil Experiment to discover the nucleus and proton. With this, he created the nuclear atom model. He believed that the atom is mostly empty space with all the positive charge within the nucleus. -
Bohr
Bohr created the Bohr Model for the atom. -
Francis Aston
Aston discovered isotpes using the mass spectrograph. -
Schrodinger
Schrodinger used math equations to find the probablity an electron would be in a certain position. He created the Quantum Mechanical atom model. -
James Chadwick
Chadwich discovered the neutron.
